This invention relates to a sealing grommet which is especially suitable for (although not so limited) to use in the unplugging of a hydrocyclone heavy fraction outlet during operation under pressure and without spillage or spraying of fluids to the outside and to hydrocyclone systems incorporating such grommets. The invention has particular application to multiple hydrocylone arrangements disposed in pressurized cannisters or arranged in banks.
The known multicyclone arrangements either do not provide such facilities or else they use one of two basic concepts in an effort to deal with the problem.
The system employed by Celleco AB is based on providing a nylon plug that can be removed entirely or else twisted in its guides to expose a hole on the extension of the hydrocyclone centre line behind the heavy fraction opening. Through this slightly oversized hole, a 1/4 inch diameter high pressure water nozzle may be inserted. By using the flushing water jet stream in combination with the ramming action of the tip of the nozzle the plugged hydrocyclone may be unplugged "on the run". The deficiency of this solution resides in the necessity of opening the nylon plug while the heavy fraction chamber or reject header is under pressure, and thus before or even during the unplugging operation there is a lot of spraying or spilling of hot fluid suspension onto the operator attempting to accomplish this task.
The Black Clawson Co. uses a special purge gun kit. When, in looking through a sight glass, the operator notices that the discharge from the hydrocyclone has ceased, it is evident that the heavy fraction discharge opening is plugged. He then pushes a purge gun needle through a soft rubber purge button and into the tip of the hydrocyclone. A blast of water at 500 psi slices through the packed heavy solids until the tip of the needle is beyond the packed plug. A combination of the water blast and vibration of the needle clears the plug. As the needle is withdrawn, the soft rubber purge button collapses behind it, sealing its exit. If any minor leakage occurs, a set screw, capable of squeezing the punctured purge button, can be tightened to stop such leakage. To obtain these sealing conditions after unplugging, the hypodermic-type purge gun needle used must be very thin, thus bending easily and supplying very little flow--just above 0.5 GPM at 500 psi. Hence, its effectiveness is rather limited in many instances.